It comes amid fears that Abedi "had help" making a "big and sophisticated bomb" that ultimately killed 22 people, it is claimed.

(Image: SWNS - Leeds SWNS.com)

Police have named British-born Salman Abedi, 22, as the bomber behind Monday's attack, which left a further 119 victims wounded.

And detectives fear an expert bomb-marker who built the deadly device before instructing Abedi to be his 'mule' could still be at large.

A police source told the Manchester Evening News : "They don't waste bomb makers. The reason we have gone to critical is because he is still out there and the fear is that he will strike again before they get caught."

Today, U.S. officials reportedly said Abedi had assistance in making the IED, which he detonated in the foyer area of the packed arena.

They also claimed concerned family members had warned security officials that he was "dangerous" ahead of the attack, NBC reports.

He added: "A US intel official tells nbcnews members of bomber's family warned sec officials about him in past, that he was 'dangerous'."

Mirror Online contacted the Home Office about the claims and was referred to Home Secretary Amber Rudd's earlier statement, in which she confirmed Abedi was known to authorities.

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Born in Manchester to parents of Libyan origin, the bomber is believed to have returned from Libya just days before the terror atrocity.

He had also previously spent time in war-torn Syria.

Today, the first picture of Abedi emerged - as an iman has revealed how the terrorist once showed him the "face of hate".

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(Image: PA)

Sheikh Mohammed Saeed said there were fears Abedi was going to attack him while he gave an anti-ISIS speech at a mosque two years ago.

"He showed me the face of hate, Salman, after that sermon," he told The Times, referring to the incident at the local Didsbury mosque.

"He used to show me the face of hate. I could tell this person hates me. You understand, it's no surprise to me [that he was the attacker]."

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He claimed Abedi - said to be a Manchester United fan and a keen cricketer - started to pray elsewhere because of how he felt.

Speaking to Mirror Online, one of Abedi's former friends, called Jason, said he was shocked by the "sickening" attack two days ago.

He said he had lived in Fallowfield, Manchester - where the bomber's parents moved to from London at least 10 years ago - all of his life.

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(Image: SWNS - Leeds SWNS.com)

Despite reports that Abedi was seen locally as "the face of hate", he said he "wouldn't have expected" his old pal to commit such an act.

"I grew up [here] all my life, knew him to say hello to and often hung around [with him] a few years ago," Jason told us.

"Can honestly say I wouldn't have expected this. It came as a shock, can't believe it, all innocent lives... it's sickening."

He added that a massive car cruise convoy would be going through the town on Sunday in tribute to the bombing victims.

"At least 2500 cars will be going to raise funds to support their families," he said.

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(Image: @SparkleMax15 /Twitter)

Another man, Kirk Crager, revealed he had met Abedi around five years ago while taking an "Intro to Islam" course at the mosque.

"I met him face to face and you never would have known. He was quiet and polite," he said.

"I'm actually both sad for him and angry as well since he was clearly misled."

He described the killer as "a sad victim of his own ideology and victimiser of so many".

Earlier today, the Home Secretary said Abedi likely did not act alone when he detonated an IED at the end of an Ariana Grande concert.

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Rudd also confirmed he was known to the authorities.

"We do know that he was known up to a point to the intelligence services," she told Sky News.

"I am sure that we will get more information about him over the next few days and the next few weeks."

Her comments came as French interior minister Gerard Collomb said Abedi had "proven" links with the Islamic State terror group.

He also told French television that both British and French intelligence services had information that Abedi had been in Syria.

(Image: Sky News)

The bomber, one of four siblings, spent three weeks in Libya before the Manchester attack, The Times reports.

A friend told the newspaper: “He went to Libya three weeks ago and came back recently, like days ago.”

There are claims that, in the hours before the attack, he had travelled by train from London to Manchester.

Abedi, thought to have been a student at Salford University, grew up near Whalley Range High School.

It is the same school of twins and formerly aspiring medical students, Zahra and Salma Halane, who left their homes and fled to Syria in 2014.

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According to school friends, Abedi, who attended the boys' school, Burnage Academy, was a keen Man Utd supporter.

Former pal Leon Hall told MailOnline he saw the killer last year and said he had grown a beard.

Hall, 26, and Abedi lived close to each other in a row of run down terraced houses in the Moss Side area of Manchester.

They later ended up living next door to each other in a nearby street and went to the same school.

People living on the red-bricked semi-detached street said they knew little about those who reside at the address.

According to neighbours, Abedi’s behaviour had become increasingly strange ahead of the suicide bombing.

He had reportedly started chanting prayers in the street.

Local Lina Ahmed said: “He was chanting in Arabic. He was saying, ‘There is only one God and the prophet Mohammed is his messenger’.”

Yesterday, the Mirror revealed how Abedi was being probed over his links to a known Islamic State recruiter from Manchester.

A team including 30 armed officers raided the suicide bomber’s home and police were seen recovering a book called Know Your Chemicals.

An investigation is currently under way into his ties with fellow Mancunian Raphael Hostey, also known as Abu Qaqa al-Britani.

Abedi was believed to be a family friend of Hostey, who persuaded hundreds of Brits to fight for ISIS in Syria.

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The fanatic was blitzed in a drone strike in May last year, aged 24.

Nearly two dozen people were killed and a further 59 were hospitalised after Abedi blew himself up at the arena on Monday.

Sixty others were described as 'walking wounded'.

The horrific attack occurred as unsuspecting fans, including thousands of kids and teenagers, left the pop concert on Monday night.

Last night, cities across the globe proudly stood shoulder-to-shoulder with Manchester - and the rest of Britain - in the wake of the atrocity.

Famous structures, including the Brandenburg Gate in Berlin, Germany, were lit up in the red, white and blue colours of the Union flag.

The Story Bridge in Brisbane, Australia, the Burj Khalifa in Dubai and the Jet d'Eau in Geneva, Switzerland, also made this gesture.

And so did the Petrin Tower in Prague, Czech Republic, The Orlando Eye in Florida, US, and Belfast City Hall in Northern Ireland.

Meanwhile, in North Adelaide, South Australia, an image of the flag was beamed onto Adelaide Oval, the Manchester Evening News reports.

Elsewhere, the huge HSBC building in Hong Kong featured a message in support of the 22 victims - ‘We stand with the United Kingdom’.

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In New York and Paris, the Empire State Building and the Eiffel Tower were plunged into darkness last night in solidarity with the victims.

The poignant gestures in major cities echoed global responses to past terror attacks in Paris, Nice, Berlin, Brussels and Stockholm.

In the wake of the latest atrocity, soldiers have been deployed to key sites across the UK to prevent further attacks.

Prime Minister Theresa May announced yesterday that the threat level was now considered "critical", meaning an attack may be imminent.

ISIS had earlier claimed responsibility for the arena atrocity.

The terror group said in a statement: “With Allah’s grace and support, a soldier of the Khilafah [caliphate] managed to place explosive devices in the midst of the gatherings of the crusaders in the British city of Manchester.”